Abstract Repeated exposure to environmental agents, such as pesticides and metals, can alter gene expression patterns, potentially resulting in enhanced susceptibility to future toxic insults. With greater than 90% of Parkinson's disease (PD) cases considered idiopathic, epidemiology has indicated the involvement of pesticides in PD. Specifically, exposures to the herbicide paraquat (PQ) and the fungicide maneb (MB) are associated with a 75-80% increased risk of PD. Additionally, epigenomic changes in gene expression are postulated to play a role in neurodegenerative disorders like PD. My previous NIEHS funded research (F32 ES019821) demonstrated that MB-potentiation of PQ neurotoxicity was not simply due to enhanced oxidative stress, but a complex mechanism involving thiol-modification by MB and oxidation by PQ. Additional gene expression data show that MB significantly altered the expression of more genes compared to PQ. MB induced 4 different amino acid transporters and 2 metal transporters. Of particular interest, Ala-, Ser-, Cys- preferring transporter-1 (ASCT-1 (Slc1a4)) and proton coupled, divalent metal ion transporter (LSH (Slc11a1)) were induced greater than 2-fold by MB and PQ+MB compared to control. The working hypothesis for this K99/R00 Career Development Award proposal is that long-term exposure to MB potentiates PQ-mediated neurodegeneration of dopaminergic neurons caused by increased uptake of PQ due to modified amino acid transporter expression, metal-mediated oxidative stress and changes in the epigenome. To accomplish this, 4 specific aims (2 mentored, 2 independent) consisting of in vitro and in vivo models will be used. In Specific Aim 1 (K99 mentored phase), both in vitro and in vivo models will be employed to determine if potentiation of PQ neurotoxicity is due to MB-mediated induction of ASCT-1 and LSH. Specific Aim 2 (K99 mentored phase) will study if methylation of genes associated with dopamine metabolism is mechanistically involved in MB- potentiated PQ neurotoxicity. Research proposed in Specific Aim 3 (R00 independent phase) will explore alterations in histone H3 methylation and acetylation caused by long term pesticide exposure. Lastly, Specific Aim 4 (R00 independent phase) will investigate global alterations in the DNA methylome in response to long term pesticide exposure. This project is designed to further develop my research program and fulfill strategic goals of the NIEHS by connecting environmental influences to disease through the study of epigenomics and to train the next generation of environmental scientists. The proposed research will meet these goals and foster the development of my independent research career.